Microwave dielectric properties of BNT-BT0.08 thin films prepared by sol-gel technique

International audienceWe report for the first time the microwave characterization of 0.92(Bi0.5Na0.5)TiO3-0.08BaTiO3(BNT–BT0.08) ferroelectric thin films fabricated by the sol-gel method and integrated in both planarand out-of-plane tunable capacitors for agile high-frequency applications and particularly on theWiFi frequency band from 2.4 GHz to 2.49 GHz. The permittivity and loss tangent of the realizedBNT-BT0.08 layers have been first measured by a resonant cavity method working at 12.5 GHz.Then, we integrated the ferroelectric material in planar inter-digitated capacitors (IDC) and in outof-plane metal-insulator-metal (MIM) devices and investigated their specific properties (dielectrictunability and losses) on the whole 100 MHz–15 GHz frequency domain. The 3D finite-elementselectromagnetic simulations of the IDC capacitances are fitting very well with their measuredresponses and confirm the dielectric properties determined with the cavity method. While IDCs arenot exhibiting an optimal tunability, the MIM capacitor devices with optimized Ir/MgO(100) bottomelectrodes demonstrate a high dielectric tunability, of 30% at 2.45 GHz under applied voltagesas low as 10 V, and it is reaching 50% under 20V voltage bias at the same frequency. These high frequencyproperties of the MIM devices integrating the BNT-BT0.08 films, combining a high tunabilityunder low applied voltages indicate a wide integration potential for tunable devices in themicrowave domain and particularly at 2.45 GHz, corresponding to the widely used industrial, scientific,and medical frequency band